The present invention relates to flame retardant compositions which are bromine and phosphorus containing polyesters, and which are particularly adapted to prevent crystallization, and exuding or oiling out such as occurs in other flame retardant methods. The present organic polymer compositions are ternary copolymers in which a bromo bisphenol alkyl or aryl phosphine oxide replaces a portion of the hydroxy component of the polyester.
Compounds of various types have been employed as flame retardant components, generally as physical additives, in various organic polymers. However, a common difficulty when using such compounds has been their incompatibility with the organic polymer base material; for example, some inorganic phosphates such as ammonium phosphate when used in polyethylene terephthalate. Other additives including organic phosphates have been found to exude out of the polymer so that the desired flame-retardant modifying effect on the organic polymer was lost.
The present ternary polymeric esters are based upon an alcoholic component such as ethylene glycol and an acidic component such as terephthalic acid. Derivatives of each of these compounds are also used in the same relationship. However, a third component, copolymerized as a part of the final ester is also present, namely bromobisphenol alkyl or aryl phosphine oxide. ##STR2## The hydroxyl groups are present in either P or m positions rel. to phosphorus,
M PLUS N IS FROM 1 TO 8, PREFERABLY 1 TO 4 AND MOST PREFERABLY 4, AND R is an alkyl radical of 1 to 10 carbon atoms, or an aryl radical of 6 to 10 carbon atoms. This bromine and phosphorus containing compound provides a synergistic flame retardant effect, while at the same time permitting the poylester to be formed by the usual polymerization and other processing steps without deleterious effects upon the fiber properties. The above products are compounds with both phosphorus and bromine present in the same molecule. These compounds are bifunctional components which copolymerize as a stable, non-degrading polymer. The prior art has used individual phosphorus and bromine components, but many of these degraded or separated out of the fiber. In contrast, the present fibers avoid crystallization of a solid phase which would prevent spinning by clogging the spinnerettes. The polyester product also retains the other desirable properties of high strength, as well as wash and wear characteristics, e.g. retention in the copolymer without washing out. The polyesters lend themselves very well to blend fabrics such as polyester/cotton and exhibit good hand and other esthetic properties. The polyester fibers also avoid degradation of the polyester so that the molecular weight is retained with good spinnability.
The resultant ternary polymers have at least 2 wt. % bromine, and preferably from 3 to 25 wt. % bromine and 0.1 to 10 wt. % phosphorus based upon the total polymer. A preferred range of phosphorus is from 0.5 to 1.5%. Control of the relative proportions of the alcohol and of the acid moieties as well as the relative molecular weight of the starting materials and of the final polymeric esters makes it possible to obtain products having properties of solubility, and melting point to provide flame retardant properties and other physical properties without the prior art difficulties of exuding or crystallization.